The number of South Korean babies with birth defects has increased significantly since the early 1990s, likely due to traffic-related air pollutants and endocrine disruptors, a study showed Monday.

The report, by Inha University’s Social and Preventive Medicine department, researched the national health insurance data of 403,250 infants aged 0-1 living in Korea’s seven metropolitan areas between 2009 and 2010. It found that 5.5 percent of all infants researched during the period had birth defects, an increase from the 3.3 percent of those born between 1993 and 1994.

Among all birth defects reported in the period of 2009-2010, hypospadias -- a birth defect of the urethra where the urinary opening is not on the head of the male genital -- had the highest increase rate of all birth defects from 1993-2010. The prevalence rate of the abnormality increased from 0.7 per 10,000 in 1993-1994 to 9.9 per 10,000 in 2009-2010. Meanwhile, the number of cases of cryptorchidism, the absence of one or both testes from the scrotum, also increased significantly from 2.6 per 10,000 to 29.1 per 10,000.

Citing overseas studies published in the past, the researchers suggested the increasing number of defects in the Korean newborns’ genital and urinary systems, such as hypospadias and cryptorchidism, may have been caused by pregnant women’s exposure to traffic-related air pollutants and endocrine disruptors such as Bisphenol A, which is primarily used to make plastics. They said that an environmental surveillance system needs to be established in South Korea to prevent birth defects.

Among all birth defects reported from 2009-2010, genital and urinary tract defects were in fact the second most common condition, with a prevalence rate of 130.1 per 10,000, following heart defects which stood at 180.8 per 10,000.

“Previous studies have suggested that the prevalence of undescended testis increased during the past half century in industrialized countries,” the paper noted.

“A study conducted in China reported an average annual increase in the overall prevalence of hypospadias of 7.34 percent from 1996 to 2008. The authors suggest that environmental exposure might play a critical role in the development of hypospadias.”

A 2013 study by Stanford University School of Medicine also found an association between traffic-related air pollutants and malformations of the brain and spine of newborns in California.

The Inha University study also suggested that exposure to endocrine disruptors -- chemicals that, at certain doses, can interfere with the hormone system in humans -- may have increased the number of newborns with birth defects in Korea. According to the paper, chemicals such as pesticides, polychlorinated biphenyls, naturally occurring plant estrogens, bisphenol A and mycotoxins have been reported to affect human pregnancies.

This correlates to a French study published last year in European Urology, which found that pregnant women who are exposed to endocrine disrupting chemicals at work, such as cleaners, hairdressers and laboratory workers, are more likely to have baby boys with a genital defect.

The Korean researchers also found that South Korea’s prevalence rate of spina bifida (7.7 per 10,000) -- a birth defect where there is incomplete closing of the backbone and membranes around the spinal cord -- is notably higher than the rates in other developed nations, such as the U.S. (3.8 per 10,000), Finland (4.62 per 10,000) and Canada (4.28 per 10,000).

The paper suggested that this may be associated with the inadequate consumption of folate acid among Korean women.

“The lack of this nutrient is known to cause spina bifida. … A recent study in Korea reported that only 10.3 percent of Korean women consume folate acid in the periconceptional period.”

Meanwhile, cases of Atrial Septal Defect, a congenital heart defect which involves a hole in the wall between the two upper chambers of the organ, also increased significantly from 9.7 per 10,000 newborns to 117.9 per 10,000, while cases of congenital polycystic kidney disease, a disorder in which clusters of cysts develop within kidneys, also increased from 0.7 per 10,000 to 29.1 per 10,000.

By Claire Lee (dyc@heraldcorp.com)